This invention relates generally to vehicle rear vision systems for providing drivers with a view rearwardly of the vehicle. The invention may find application with optical rearview mirror assemblies and with solid-state-imaging arrays which capture images rearwardly of the vehicle for display by a display device.
With the advent of electro-optic mirror systems, in which an electro-optic reflectance element is driven to a partial reflectance level by a control module which is responsive to light levels in and around the vehicle, the vehicle rearview mirror has become an electronic assembly. Additional elements, such as motorized positioning devices, or actuators, for the mirror as well as mirror heaters, further contribute to the electrical functions performed by a mirror assembly. These functions require a one-way flow of control information to the mirror assembly. More recent features, such as multiple mirror position memory, require a two-way communication flow. The memory mirror assembly includes a position encoder which communicates the position of the mirror to a memory controller, typically located remotely from the mirror, such as at the vehicle dash. Other two-way communication flows are required by the addition of other features in the rearview mirror, such as keyless entry systems and the like. Other features are being added to vehicle mirrors, in general, and exterior mirrors, in particular, such as remote-actuated exterior vehicle security lights and signal lights, such as disclosed in commonly assigned U.S. Pat. Nos. 5,371,659 and 5,497,305 for REMOTE ACTUATED EXTERIOR VEHICLE SECURITY LIGHT; global positioning system antennas and/or receivers, as disclosed in commonly assigned International Application WO 97 21127 published Dec. 6, 1996, by Roger L. Veldman and Desmond J. O'Farrell for a VEHICLE GLOBAL POSITIONING SYSTEM NAVIGATIONAL AID; and blind spot detection systems, such as disclosed in U.S. patent application Ser. No. 60/013,941 filed Mar. 22, 1996, by Kenneth (NMI) Schofield for PROXIMITY DETECTION OF OBJECTS IN AND AROUND A VEHICLE, the disclosures of which are hereby incorporated herein by reference. Various other electronic functions, including heading sensors, better known as electronic compasses, intrusion detection and other security systems, antennas for intelligent vehicle highway systems (IVHS), as well as various transmitting and/or receiving antennas and/or systems including garage door openers, cellular telephones, radios, and the like are candidates for positioning within a mirror assembly.
Even with the moderate level of electrification of present vehicle mirror assemblies, it is not uncommon to require as many as 20 wire leads extending to the exterior mirror assemblies. This creates the problem of guiding the wire harness, including a connector, through the door panel. Additionally, the wiring harness adds weight to the vehicle and greatly increases the labor assembly time of the vehicle.
It has been proposed to replace the exterior mirror system of a vehicle with solid-state-imaging arrays which capture images rearwardly of the vehicle for display by a display device on or near the vehicle dash. One such system is disclosed in commonly assigned U.S. Pat. No 5,670,935 issued to Kenneth (NMI) Schofield, Mark L. Larson and Keith J. Vadas for a REARVIEW VISION SYSTEM FOR VEHICLE INCLUDING PANORAMIC VIEW, the disclosure of which is hereby incorporated herein by reference. In such a rearview vision system, the solid-state-imaging device may be positioned in a housing in the approximate vicinity of present exterior rearview mirrors. As such, it can be expected that many of the electrical functions being placed in the housing of existing and proposed rearview mirror assemblies will be placed in the housing of the solid-state-imaging array in such system.
The increase in electronic functions being performed through the vehicle rearview assembly increasing involves communication with other portions of the vehicle. For example, global positioning system (GPS) functions and intelligent vehicle highway system (IVHS) functions may interact with other modules controlling vehicle navigation and the like. A headlamp control of the type disclosed in commonly assigned U.S. Pat. No 5,715,093 issued to Kenneth L. Schierbeek and Niall R. Lynam, for an AUTOMATIC REARVIEW MIRROR SYSTEM WITH AUTOMATIC HEADLIGHT ACTIVATION, the disclosure of which is hereby incorporated herein by reference, utilizes common light sensors for activating the vehicle's headlights and establishing a partial reflectance level for the electro-optic mirror element. Such feature requires interaction with a headlamp module. Keyless entry systems may interact with the vehicle door locks, as well as interior lighting systems. Blind spot detection, intrusion detection, as well as numerous other functions, may involve interaction with various modules associated with the vehicle dash. Therefore, the vehicle mirror system is becoming more integrated with the rest of the vehicle electronics. A variety of other functions can be integrated into the interior or exterior mirror housing. For example, an electronically trainable garage door opener may be included, such as is described in U.S. Pat. No. 5,479,155 issued to Zeinstra et al.
In order to minimize hardware cost and overhead, as well as provide flexibility for expansion and technological advancements in vehicle electronics, vehicles are increasingly being equipped with serial data communication networks. Such networks include a bidirectional serial multiplex communication link over a bus among a plurality of control modules, each containing a microprocessor or microcomputer. Messages are transmitted asynchronously with priorities assigned to particular messages. For example, messages which require immediate access to the bus for safety reasons are provided top priority, with messages that require prompt action in order to prevent severe mechanical damage to the vehicle provided with a lesser priority but a higher priority than messages that affect the economical or efficient operation of the vehicle. The protocol of the system provides that higher priority messages are communicated without delay while lower priority messages await communication of higher priority messages. An industry standard for such serial data communication network is SAEJ1708 published October, 1993.
Functions associated with rearview mirror assemblies have traditionally not been included on the vehicle communication network. Almost all of the traditional mirror functions would be assigned lowest priority and would, therefore, have to await transmission of higher priority messages. Therefore, the traditional approach has been to provide dedicated hardware interconnects between devices located in the rearview mirror assemblies and external devices, such as power sources, switches, controls, and the like. One solution is proposed in U.S. Pat. No. 5,196,965 entitled REARVIEW UNIT FOR MOTOR VEHICLES in which a multiplex data system communicates information between a control unit and at least one exterior rearview mirror. While such system reduces the wire count extending through the door, or doors, to the exterior mirrors, it fails to fully integrate functions associated with the mirror assemblies with the remaining electronic assemblies of the vehicle.
Vehicle memory mirror systems include encoders for monitoring the position of each mirror element with respect to typically two axes and a positioning device, such as an actuator, for selectively positioning the mirror element with respect to those axes. A control unit, typically located in and about the dash or in the door assembly, is capable of storing multiple data sets, each of which establishes a particular position of one or more of the vehicle's mirror elements. In this manner, when a different driver operates the vehicle, the data set associated with the driver is retrieved and utilized to position the mirror element, or elements, according to that data set. In order to do so, it is necessary to have information regarding the actual position of the mirror, which is provided by the position encoder, in order to enable the control to properly position the mirror element or elements. Such memory mirror systems further contribute to the wiring problem associated with rearview mirrors. The signals from the position encoder require additional wire leads, and all mirror assemblies included in the system must be wired back to a processor which is typically located in the dash. Furthermore, a user input device, such as a joystick, must be provided for use with each of the mirror elements of the memory mirror system in order to allow each driver to adjust each mirror element and store the position of that mirror element for that driver. This is a rather cumbersome process that can be distractive if performed while the vehicle is being operated.